In the conventional protective devices for a communication system, the jack board and plug-in protector have not necessarily been miniaturized to a satisfactory degree, so that where jack boards and plug-in protectors for accommodating several ten thousands to several hundred thousands of circuits were to be set in a system, there would be required an exceedingly large space for mounting thereof.
Also, because of a large number of parts required for constituting each unit of such jack boards and plug-in protectors in a conventional communication protective device, there were involved many steps for assemblage.
Further, since the outside line side terminals and the interior line side terminals in the conventional jack board were contrary to each other in the order of arrangement, there could be caused mis-wiring in line connections.
In the conventional jack board for a communicational protective device, in case no plug-in protector was provided, both the outside line side and interior line side of the circuit were kept open, and in case plug-in protectors were provided, both sides of the circuit were connected through said protectors. Therefore, such a jack board was useless where a non-break mechanism is required for connecting outside wiring and interior wiring of the circuit in case no plug-in protector was provided.